Pressure sensitive signal generator using piezoelectric coating

Abstract

The construction and method of operating a signal generator which provides an electrical output in response to an input mechanism such as a loading by finger are disclosed. The generator has the appearance of a plate and includes a sandwich structure comprising a conductive substrate, a coating of piezoelectric material and usually a plurality of discrete electrodes joined to the exposed surface thereof. The coating is deposited on the substrate as a slurry and is chemically bonded to the substrate. In order to produce an electrical output signal, prescribed locations on the plate are subjected to a force such as can be applied by the touch of a finger and a voltage is generated across the piezoelectric coating between the point of contact on the substrate and the adjacent electrode. The output signal is used either directly or after being amplified to drive various functionally responsive devices.

Having thus described a typical embodiment of my invention, that which I claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. An electrical signal generator comprising: a substrate of conductive material which forms a first electrode;   a coating of piezoelectric material including an interbonded mixture containing phosphorous, zirconium, titanium and chromium chemically bonded to one side of the substrate by the attachment of phosphate ions in the mixture to the substrate due to ionic bonding;   a region of conductive material which is joined to the exposed surface of the piezoelectric material and forms a second electrode; and   electrical conduction means attached to the first electrode and the second electrode to conduct away as useful electrical signals, electric pulses established across the piezoelectric material due to force applied to the substrate.   
     
     
       2. The invention according to claim 1 wherein a plurality of regions of conductive material which is isolated from each other are formed on the exposed surface of the piezoelectric material forming a plurality of discrete second electrodes and electrical conduction means are attached to each of the second electrodes. 
     
     
       3. The invention according to claim 2 including further means for covering the exposed surfaces of the piezoelectric material to prevent contamination thereof. 
     
     
       4. The invention according to claim 3 wherein the covering is an elastomeric material. 
     
     
       5. The invention according to claim 4 including further a frame which supports the substrate along its edges. 
     
     
       6. The invention according to claim 5 wherein the substrate is a thin sheet of metal. 
     
     
       7. The invention according to claim 2 including further a base which is held by the frame assembly adjacent to the ceramic material to support the substrate, the base having depressions adjacent to each of the second electrodes to allow the substrate to be displaced to the direction of the base without interference. 
     
     
       8. The invention according to claim 7 wherein the exposed surface of the substrate adjacent to each of the second electrodes is visibly designated. 
     
     
       9. The invention according to claim 8 including further a flexible covering on the flat surface of the substrate without the piezoelectric coating. 
     
     
       10. The invention according to claim 9 including further a signal processor which receives the electric pulses from the conduction means and provides an output signal. 
     
     
       11. The invention according to claim 10 including further an auxiliary power source which receives the output from the signal processor and amplifies the power thereof. 
     
     
       12. An electrical signal generator comprising: a structural member comprising a resilient substrate of conductive material which is rigid and flexes under the force ordinarily provided from contact with a pressing finger, and forms a first electrode;   a coating of piezoelectric material including an interbonded mixture containing phosphorous, zirconium, titanium and chromium chemically bonded to one side of the substrate by the attachment of phosphate ions in the mixture of the substrate due to ionic bonding;   a region of conductive material which is joined to the exposed surface of the piezoelectric material and forms a second electrode; and   electrical conduction means attached to the first electrode and the second electrode to conduct away as useful electrical signals electric pulses established across the piezoelectric material as a result of flexing of the substrate due to forces applied thereto.   
     
     
       13. A signal generator comprising: a substrate which forms a common electrode;   a coating of piezoelectric material deposited on the substrate as a slurry and dried at a temperature sufficient to allow the coating which includes an interbonded mixture containing phosphorous, zirconium, titanium and chromium to adhere to the substrate by the attachment of phosphate ions in the mixture to the substrate due to ionic bonding;   a second electrode which is formed on the exposed surface of the piezoelectric coating; and   electrical connection means attached to the second electrode.   
     
     
       14. The invention according to claim 13 including further additional second electrodes so disposed on the exposed surface of the piezoelectric coating that each is isolated from the other, and additional electrical connection means formed to the additional second electrodes to allow individual electrical contact with each of the second electrodes. 
     
     
       15. A signal generator comprising: a structural member comprising a resilient metal substrate which forms a common electrode, is rigid, flexible and electrically conductive;   a coating of piezoelectric material deposited on the substrate as a slurry and dried at a temperature sufficient to allow the coating which includes an interbonded mixture containing phosphorous, zirconium, titanium and chromium to chemically bond to the substrate by the attachment of phosphate ions in the mixture to the substrate due to ionic bonding;   a second electrode which is formed on the exposed surface of the piezoelectric coating; and   electrical connection means connected to the second electrode.